1. Field of the Invention
The present invention generally relates to a spine formation device to form a spine of a bundle of folded sheets, a post-processing apparatus including the spine formation device, and a spine formation system including the spine formation device, and an image forming apparatus, such as a copier, a printer, a facsimile machine, or a multifunction machine capable of at least two of these functions, that includes any of those devices.
2. Discussion of the Background Art
Post-processing apparatuses that fold and/or bind together a bundle of sheets of recording media (hereinafter “booklet”) are widely used.
When the spine of the booklet is flattened, bulging of the booklet can be reduced, and accordingly multiple booklets can be piled together. This reformation is important for ease of storage and transport because it is difficult to stack booklets if their spines bulge, making it difficult to store or carry them. For example, the bulging spine of the booklet can be flattened using a pressing member configured to sandwich an end portion of the booklet adjacent to the spine and a spine-forming roller configured to rotate along the spine of the booklet in a longitudinal direction of the spine while contacting the spine of the booklet. The spine-forming roller moves at least once over the entire length of the spine of the booklet fixed by the pressing member while applying a pressure sufficient for flatten the spine to it. Additionally, an amount by which the spine of the booklet projects from the pressing member can be set by a stop plate disposed facing the spine of the booklet, configured to move toward and away from the spine of the booklet.
However, in this configuration, although the spine-forming roller contacts the spine of the booklet linearly or in a small contact area while moving and applying pressure to the spine of the booklet to flatten it, the pressure necessary to flatten the spine tends to change constantly and significantly. The change in the pressure to flatten the spine causes a relative distance between the spine-forming roller and the spine of the booklet to fluctuate constantly. As a result, the spine can be wavy in the longitudinal direction of the spine even though the spine is straightened in the direction of the thickness of the booklet.
Additionally, although the stop plate sets an amount by which the booklet projects from
the pressing member, that is, sets the position of the booklet, the stop plate does not contribute to flattening the spine.
In view of the foregoing, the inventor of the present invention recognizes that there is a need to form the spine of the booklet with a higher degree of flatness, which known approaches fail to do.